JP2002310646A - Angular displacement detector for joint actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, lightweight, and low-profile angular displacement detector for detecting absolute angular displacement, with high accuracy in a non-contacting manner. SOLUTION: This angular displacement detector 1 comprises a rotating body 2 rotating about a prescribed rotational axis 2 and a distance sensor 3 for detecting a radial gap d left by the outer circumference of the rotating body 2 in a non-contacting manner. Since the shape of the rotating body 2 is determined, so that the gap d between the sensor 3 and the outer circumference of the rotating body 2 changes, depending on a rotation angle θ of the rotating body 2, the rotational position the angular displacement of the rotating body 2 can be detected, based on the gap d as for as to the outer circumference of the rotating body 2 and measured by the sensor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular displacement detecting device for detecting an angular displacement of a rotating body, and more particularly to an angular displacement detecting device for detecting an absolute angular displacement of a shaft of a motor used as an actuator.

More specifically, the present invention relates to an angular displacement detecting device for detecting an absolute angular displacement of a shaft of a motor used as a joint actuator of a legged mobile robot, and more particularly to a non-contact and highly accurate absolute angular displacement detecting device. To detect,
The present invention relates to a small, lightweight, and thin angular displacement detection device.

[0003]

2. Description of the Related Art A mechanical device that performs a motion similar to a human motion by using an electric or magnetic action is called a "robot". The robot is derived from the Slavic word "ROBO"
TA (slave machine) is said to have come from. In Japan, robots began to spread from the late 1960's, but most of them were based on automation of production work in factories.
These were industrial robots such as manipulators and transfer robots for unmanned purposes.

[0004] A stationary type robot such as an arm type robot which is implanted and used in a specific place,
Active only in fixed and local work spaces such as parts assembly and sorting work. On the other hand, the mobile robot has a work space that is not limited, and can freely move on a predetermined route or on a non-route to perform a predetermined or arbitrary human work, or perform a human or dog operation. Alternatively, a wide variety of services that replace other living things can be provided. Among them, legged mobile robots are unstable and difficult to control their posture and walking compared to crawler and tired robots. It is excellent in that a flexible walking / running operation can be realized regardless of the type.

Recently, a pet-type robot that simulates the body mechanism and operation of a four-legged animal such as a dog or a cat, or a body mechanism or movement of an animal such as a human that walks upright on two legs has been modeled. "Humanoid" or "humanoid" robot (humanoid r)
obot), research and development on legged mobile robots is progressing, and expectations for practical use are increasing. For example, Sony Corporation announced a bipedal humanoid robot "SDR-3X" on November 25.

[0006] This type of legged mobile robot generally has a large number of degrees of freedom of joints and controls the movement of joints by an actuator.
It is realized by a motor. Also, by taking out the rotation position, rotation amount, etc. of each motor and performing servo control, while reproducing the desired operation pattern,
Attitude control is performed.

The fact that the mobile robot is composed of a large number of joint actuators as described above means that in order to faithfully reproduce the operation pattern and to stabilize the attitude to a high degree, the motors provided at the joints are required. This means that the rotation angle of the shaft needs to be measured accurately. For example,
In the case of a two-legged walking type legged mobile robot, the position of the center of gravity is high, and the ZMP (Zero Moment Point) stability area is narrow. The absolute angular displacement of the motor shaft must be detected (for the concept of ZMP and the point where ZMP is applied to the stability discrimination standard of walking robots,
"LEGGED LOCOMOTION ROBOTS" by Miomir Vukobratovic
(It is described in Ichiro Kato, "Walking Robot and Artificial Feet" (Nikkan Kogyo Shimbun)).

In addition, the weight, volume,
In addition, considering the weight balance and the like, it is desirable that the angle detecting device for each joint actuator be small, light, and thin.

Conventionally, potentiometers, optical rotary encoders, magnetic resolvers, and the like can be cited as absolute angular displacement sensors.

A potentiometer has a theoretical resolution of infinity, but has a short life due to wear and the like because it is a contact type sensor having a contact portion in a variable resistance portion. In many cases, the contact-type structure uses the same, and the mechanical life of the slider is short.)

The optical rotary encoder is of a non-contact type and can detect a rotation angle by a digital value. However, in order to increase the resolution, the sensor swells in the thickness direction, which is not suitable for miniaturization. In addition, since it is not analog amount detection, when digital differentiation (difference) is performed to obtain a speed component, the resolution at the time of low-speed rotation is reduced.

The magnetic resolver is of a non-contact type, detects a rotation angle with multiple analog outputs, and calculates an angle by an inverse operation of a trigonometric function. However, in order to increase the resolution, it expands in the thickness direction, so it is not suitable for miniaturization. In addition, since the calculation of the angle calculation is indispensable, the detection time becomes longer unless a dedicated calculator is mounted. If the detection time is slow, the sample time will be delayed,
Servo control does not work well.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent angular displacement detecting device capable of detecting the absolute angular displacement of a shaft of a motor used as an actuator with high accuracy.

A further object of the present invention is to provide an excellent angular displacement detecting device capable of detecting the absolute angular displacement of a shaft of a motor used as a joint actuator of a legged mobile robot with high accuracy. .

A further object of the present invention is to provide a small, lightweight, thin, and excellent angle capable of detecting the absolute angular displacement of a shaft of a motor used as a joint actuator of a legged mobile robot in a non-contact manner with high accuracy. An object of the present invention is to provide a displacement detection device.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and is directed to an angular displacement detection device for detecting an angular displacement of a shaft of a motor used as a joint actuator. A rotating body mounted coaxially with a motor shaft to be inspected,
A sensor for measuring a gap to an outer periphery of the rotating body, wherein a radius of the rotating body is changed such that an angular displacement of the rotating body and a gap to the sensor have a unique relationship. Angular displacement detecting device for a joint actuator.

The angular displacement detecting device according to the present invention comprises a rotating body that rotates around a predetermined rotation axis, and a sensor that detects a radial gap to the outer periphery of the rotating body 2 in a non-contact manner. Is mounted coaxially with the shaft of a joint actuator / motor of a robot, for example.

Gap d from sensor to outer periphery of rotating body
However, since the shape of the rotating body is determined so as to change according to the rotating angle θ of the rotating body, the rotational position or angle of the rotating body is determined based on the gap d to the outer periphery of the rotating body measured by the sensor. Displacement can be detected.

Since the angular displacement detecting device according to the present invention is a non-contact detecting system, a long life can be expected.

The sensor is, for example, a reflection type sensor composed of a combination of a light emitting element for irradiating the outer periphery of the rotating body with invisible light and a light receiving element for receiving light reflected from the outer periphery of the rotating body. Can be configured.

Since the optical sensor used for the light receiving element can be easily reduced in size in general, it can contribute to the reduction in size, weight, and thickness of the entire detection system and the joint actuator.

An optical sensor generally has a detection distance characteristic represented by a logarithmic function. Therefore, when the outer peripheral shape is formed so that the relationship between the radius and the rotation angle of the rotating body is defined by a linear function, the detection distance characteristic of the angular displacement detection device is drawn as a logarithmic curve. Become. On the other hand, when the outer peripheral shape of the rotating body is formed so that the relationship between the radius and the rotation angle is defined by an exponential function, a linear detection distance characteristic can be given to the angular displacement detection device. That is, by selecting an arbitrary function shape, it is possible to obtain a function value corresponding to the shape.

Further, since the accuracy of the angular displacement detecting device according to the present invention depends only on the machining accuracy of the side surface shape of the rotating body, it is easy to improve the accuracy and control the variation.

Further, the angular displacement detecting device according to the present invention comprises:
Since the detection is based on the analog amount, an angular velocity and an angular acceleration component signal can be easily generated by adding a differentiating circuit. In other words, the angular displacement detection device according to the present invention can easily generate an output signal that is small, thin, has high resolution, has a long service life, and is suitable for servo control.

The rotating body is divided in a magnetization transfer direction into a magnetized portion and a non-magnetized portion other than the magnetized portion, and whether or not the outer periphery of the rotating body is a magnetized portion is determined. May be further provided.

When only the reflection type distance sensor is used, the output V has a logarithmic detection distance characteristic. The change is gradual and the resolution is reduced.

Therefore, by using the outputs of both the reflection type sensor and the magnetic sensor in combination, the absolute value of the rotation angle of the rotating pair can be detected with a high resolution.

Still other objects, features and advantages of the present invention are:
It will become apparent from the following more detailed description based on the embodiments of the present invention and the accompanying drawings.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows a basic configuration of an angular displacement detecting device 1 according to one embodiment of the present invention. As shown in FIG. 1, the angular displacement detection device 1 includes a rotating body 2 that rotates around a predetermined rotating shaft 2 and a distance sensor 3 disposed near a side surface of the rotating body 2.

The rotating shaft of the rotating body 2 is integrally mounted on a shaft (not shown) of the motor whose angular displacement is to be detected so as to rotate coaxially with the shaft.

The distance sensor 3 is constituted by a non-contact sensor element for detecting a radial gap d to the outer periphery of the rotating body 2.

In the present embodiment, the length of the radius r of the rotating body 2, that is, the gap d from the distance sensor 3 to the outer periphery of the rotating body 2 changes according to the rotating angle θ of the rotating body 2 (or the rotating angle θ). And the gap d have a unique relationship), the shape of the rotating body 2 is determined. In the example shown in FIG. 1, the rotating body 2 is formed in a cam shape.

Therefore, based on the gap d measured by the distance sensor 3 to the outer periphery of the rotating body 2, the rotating body 2
That is, the rotational position or angular displacement of the motor shaft can be detected.

As the distance sensor 3, for example, a reflection type sensor that measures a distance based on reflected light of light applied to a measurement object can be used. In this case, it is preferable that a material such as aluminum is mirror-finished, white-painted, or aluminum-deposited on the outer peripheral portion of the rotating body 2 to be measured in order to obtain good reflected light.

FIG. 2 schematically shows a circuit configuration example of the reflection type distance sensor 3. In the example shown in the figure, the distance sensor 3 is a non-visible LED (Light Emitting Diode) 31.
And the photo transistor 32 are connected in series.

When a forward current _If (A) is applied to the invisible LED 31, invisible light is emitted. The outer peripheral portion of the rotating body 2 reflects this invisible light.

When the phototransistor 32 receives the reflected light from the outer periphery of the rotator 2, it generates a photocurrent (relative collector current) I _c (A) corresponding to the intensity of the received light. The received light intensity corresponds to the gap d to the outer peripheral reflecting surface of the rotating body 2. Therefore, the photocurrent I _c output from the distance sensor 3
Is converted to a voltage and subjected to a predetermined arithmetic processing,
The gap d up to the outer peripheral reflection surface of the rotating body 2 can be obtained.

FIG. 3 shows the reflection type distance sensor 3
Distance d to launch surface and photocurrent I_cDetection distance indicating the relationship with
It shows separation characteristics. However, forward power to the invisible LED 31
Style I _f= 10 mA and the emitter voltage V_CE= 2V,
Ambient temperature T_a= 25 ° C., and the reflection surface
Assume that the emission rate is 90% white. In the example shown in FIG.
After the peak around the distance d ≒ 0.7 mm, the sensor 3
It turns out that it has a logarithmic detection distance characteristic.

As described above, the mechanism for detecting the angular displacement of the rotating body 2 based on the distance d obtained from the output of the distance sensor 3 is based on the length of the radius of the rotating body 2, that is, the rotation from the distance sensor 3. The gap d up to the outer periphery of the body 2
This is realized by the fact that the shape of the rotating body 2 is determined so as to change according to the rotation angle of (or the rotation angle and the gap d have a unique relationship).

FIG. 4 shows an example of the shape of the rotating body 2. Rotation angle θ and radius r of the rotating body 2-1 of this example
Is as shown in the following equation.

[0042]

(Equation 1)

In this example, the radius r and the rotation angle θ of the rotating body 2-1 are defined by a linear function. Therefore, as shown in FIG. 5, the output characteristic of the reflection type distance sensor 3 draws a logarithmic curve directly reflecting the detection distance characteristic shown in FIG. At this time, the relationship between the output V of the distance sensor 3 and the rotation angle θ of the rotating body 2 is represented by the following equation. However, both A and B are constants specific to the distance sensor 3, and
β is a constant unique to the sensor (offset that absorbs characteristics of an approximate region that is not logarithmic).

[0044]

(Equation 2)

FIG. 6 shows another example of the shape of the rotating body 2. The relationship between the rotation angle θ and the radius r in the rotating body 2-2 of this example is as shown in the following equation.

[0046]

(Equation 3)

In this example, the radius r and the rotation angle θ of the rotating body 2-2 are defined by exponential functions. Therefore, the output characteristics of the reflection type distance sensor 3 have a linear characteristic as shown in FIG. The output V of the distance sensor 3 at this time
And the rotation angle θ of the rotating body 2 are as shown in the following equation.

[0048]

(Equation 4)

In the above equation, A is a constant determined by a combination of the approximate cam shape of the rotating body 2 and the distance sensor 3. More specifically, the constant A is a value corresponding to the base of the logarithm in the logarithmic output characteristic originally possessed by the distance sensor 3 and the dimension (D + d) / cam shape of the rotating body 2.
It is determined by the value of D.

As described with reference to FIGS. 4 to 7, according to the angular displacement detecting device 1 according to the present embodiment, the input of the angular displacement θ of the rotating body 2 and the output voltage V from the distance sensor 3 Can be arbitrarily set according to the cam shape of the rotating body 2.

FIG. 8 schematically shows a basic configuration of an angular displacement detecting device 10 according to another embodiment of the present invention.
As shown in FIG. 1, the angular displacement detection device 10 includes a rotating body 12 that rotates around a predetermined rotation axis 2 and two non-contact type distance sensors disposed near the side surface of the rotating body 12. 131 and 132.

The rotating shaft of the rotating body 12 is integrally mounted on a shaft (not shown) of a motor whose angular displacement is to be detected so as to rotate coaxially with the shaft. In order to obtain good reflected light, it is preferable that a material such as aluminum is mirror-finished, white painted, or aluminum-deposited on the outer peripheral portion of the rotating body 12 (same as above).

The rotating body 12 according to this embodiment is configured by a combination of a magnetized portion 121 and a non-magnetized portion 122. In the example shown in FIG. 8, the magnetized portion 121 and the non-magnetized portion 12
Numeral 2 is a semicircular structure, and bisects the rotating body 12 according to the rotation angle θ. In the illustrated example, the magnetized portion 121 and the non-magnetized portion 122 have the same cam shape, but the gist of the present invention is not necessarily limited to this.

One non-contact distance sensor 131 is shown in FIG.
The reflection type distance sensor may be a combination of a non-visible LED and a photodiode similar to that shown in FIG.

The length of the radius r of the rotating body 12, that is, the gap d from the distance sensor 131 to the outer circumference of the rotating body 12 is
Since the shape of the rotating body 12 is determined so as to change according to the rotating angle θ of the rotating body 12 (or the rotating angle and the gap d have a unique relationship), the rotation measured by the distance sensor 131 is determined. Based on the gap d to the outer periphery of the body 2, the rotational position or angular displacement of the rotating body 12, that is, the shaft of the motor can be detected.

However, the reflection type distance sensor 131 is not shown in FIG.
Has already been described with reference to FIG. 2, since it has a logarithmic detection distance characteristic, the radius r of the rotating body 12 and the rotation angle θ are linear functions as shown in [Equation 1] above. When the cam shape is defined, the relationship between the output V of the distance sensor 131 and the rotation angle θ of the rotating body 2 is also a logarithmic output curve (see FIG. 5). In such a case,
At a rotational position where the distance between the distance sensor 131 and the outer peripheral reflecting surface of the rotating body 12 is increased, the change in the output V accompanying the change in the rotation angle θ is gradual, and the resolution is reduced.

The other distance sensor 132 is a non-contact distance sensor using a magnetic sensor such as a Hall element, but plays a role of compensating for a decrease in resolution of the one reflection type distance sensor 131.

FIG. 9 schematically shows a circuit configuration example of the other distance sensor 132. As shown in the figure, the distance sensor 132 includes a magnetic sensor 132-1 that generates a voltage corresponding to the magnetic field strength, a reference potential 132-2, an output potential of the magnetic sensor 132-1 and a reference potential 132-2. And a comparator 132-3 that compares the signals by positive feedback.

The distance sensor 132 outputs a high-level signal when facing the magnetized portion 121 of the rotating body 12, and outputs a low-level signal when facing the non-magnetized portion 122.
Outputs a level signal.

FIG. 10 shows the output characteristics of the distance sensor 131 and the distance sensor 132. However, the rotating body 12
It is assumed that both the magnetized portion 121 and the non-magnetized portion 122 have a cam shape in which the radius r and the rotation angle θ are defined as linear functions.

By using the outputs of both the distance sensor 131 and the distance sensor 132 in combination, it is possible to detect the absolute value of the rotation angle θ of the rotating body 12 and increase the resolution to detect the angular displacement of the rotating body 12. it can.

[Supplement] The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiment without departing from the spirit of the present invention. That is, the present invention has been disclosed by way of example, and should not be construed as limiting. In order to determine the gist of the present invention, the claims described at the beginning should be considered.

[0063]

As described above in detail, according to the present invention,
An excellent angular displacement detection device capable of detecting the absolute angular displacement of a shaft of a motor used as an actuator with high accuracy can be provided.

Further, according to the present invention, it is possible to provide an excellent angular displacement detecting device capable of detecting the absolute angular displacement of a motor shaft used as a joint actuator of a legged mobile robot with high accuracy. .

Further, according to the present invention, a small, lightweight, thin and excellent angle capable of detecting the absolute angular displacement of a shaft of a motor used as a joint actuator of a legged mobile robot in a non-contact manner with high accuracy. A displacement detection device can be provided.

Since the angular displacement detection device according to the present invention is a non-contact detection system, a long life can be expected. In addition, since both the optical sensor and the magnetic sensor can be easily reduced in size, it can contribute to the reduction in size, weight, and thickness of the entire detection system and joint actuator.

Further, since the accuracy of the angular displacement detecting device according to the present invention depends only on the machining accuracy of the side surface shape of the rotating body, it is easy to improve the accuracy and control the variation.

Further, the angular displacement detecting device according to the present invention
Since the detection is based on the analog amount, an angular velocity and an angular acceleration component signal can be easily generated by adding a differentiating circuit. In other words, the angular displacement detection device according to the present invention can easily generate an output signal that is small, thin, has high resolution, has a long service life, and is suitable for servo control.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a basic configuration of an angular displacement detection device 1 according to the present invention.

FIG. 2 is a diagram schematically illustrating a circuit configuration example of a reflection type distance sensor 3;

FIG. 3 is a diagram showing detection distance characteristics of a reflection type distance sensor 3;

FIG. 4 is a diagram showing an example of a shape of a rotating body 2.

FIG. 5 is a diagram showing output characteristics of a distance sensor 3 when the rotating body 2-1 shown in FIG. 4 is used.

FIG. 6 is a view showing another example regarding the shape of the rotating body 2.

7 is a diagram showing output characteristics of a distance sensor 3 when the rotating body 2-2 shown in FIG. 6 is used.

FIG. 8 is a diagram schematically showing a basic configuration of an angular displacement detection device 10 according to another embodiment of the present invention.

FIG. 9 is a diagram schematically illustrating a circuit configuration example of the other distance sensor 132.

FIG. 10 is a diagram showing output characteristics of a distance sensor 131 and a distance sensor 132.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Angular displacement detection device 2 ... Rotating body 3 ... Distance sensor 31 ... Invisible LED 32 ... Phototransistor 10 ... Angular displacement detecting device (other embodiment) 12 ... Rotating body 121 ... Magnetic unit, 122 ... Non-attachment Magnetic part 131 ... Reflection type distance sensor 132 ... Magnetic sensor type distance sensor 132-1 ... Magnetic sensor, 132-2 ... Reference potential 132-3 ... Comparator

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Claims (5)

[Claims] An angular displacement detecting device for detecting an angular displacement of a shaft of a motor used as a joint actuator, comprising: a rotating body coaxially mounted on a motor shaft to be inspected; A sensor for measuring a gap to the outer periphery of the body, wherein the radius of the rotating body is changed such that the angular displacement of the rotating body and the gap to the sensor have a unique relationship. An angular displacement detection device for a joint actuator, comprising: 2. A reflection type sensor comprising a combination of a light emitting element for irradiating invisible light to the outer periphery of the rotating body and a light receiving element for receiving light reflected from the outer periphery of the rotating body. The angular displacement detection device for a joint actuator according to claim 1, wherein: 3. The angular displacement detection device for a joint actuator according to claim 1, wherein the relationship between the radius of the rotating body and the rotation angle is defined by a linear function. The angular displacement detection device for a joint actuator according to claim 1, wherein the relationship between the radius of the rotating body and the rotation angle is defined by a linear function. 4. The angular displacement detection device for a joint actuator according to claim 1, wherein a relationship between a radius of the rotating body and a rotation angle is defined by an exponential function. 5. The rotating body is divided in a magnetization transfer direction into a magnetized portion and a non-magnetized portion other than the magnetized portion, and further determines whether or not the outer periphery of the rotating body is a magnetized portion. The angular displacement detecting device for a joint actuator according to claim 1, further comprising a magnetic sensor for detecting.